Valve arrangement and valve guide

ABSTRACT

A valve arrangement for supplying air to an internal combustion engine includes a first valve and a second valve arranged within the first valve. A valve guide for use in a valve arrangement is also provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.15/755,332, filed Feb. 26, 2018, which is a 371 application ofInternational Application No. PCT/EP2015/078857, filed Dec. 7, 2015,which claims priority to International Application No.PCT/EP2015/070560, filed Sep. 9, 2015.

BACKGROUND AND SUMMARY

The invention relates to a valve arrangement for supplying air to aninternal combustion engine. The invention further relates to a valveguide for such a valve arrangement.

In connection with combustion engines, turbo chargers are often utilizedwhich comprise a turbine which is driven by the flow of exhaust gases.The energy which is thus absorbed by the turbine is then transferred viaa shaft to a compressor which is arranged to compress the air on theintake side of the combustion engine and thus increase the amount of airin the combustion chamber. This means that a larger amount of fuel canbe fed to a combustion chamber in an engine, thus increasing the torqueand power of the engine.

In turbocharged diesel engines intended for, for example, commercialvehicles the available torque from the engine during take-off is oftensomewhat inadequate. The reason for this is that an engine equipped witha turbocharger performs worse than a normally aspirated engine at lowrpm's due to that the turbo charger is a hindrance of the aspiration.The fact that the engine has a take-off performance which is worse thana normally aspirated engine means that the amount of air which istypical for a turbocharged diesel engine is not supplied. This in turnmeans that the amount of fuel which is injected in the engine must belimited at low rpm's, in order to minimize the amount of smoke fromincomplete combustion due to lack of air. The turbo charger will withincreased exhaust energy supply an additional amount of air which willpermit an increased amount of fuel and by that increased engine torqueand engine power.

The above-mentioned sequence of events is furthermore unfavorable sinceit contributes to reduced performance during the take-off phase of theengine. The engine will furthermore be perceived by users as“insufficient” during the take-off phase, since it has been necessary tolimit the amount of fuel supplied during the initial “aspirating engine”phase, also known as turbo-lag.

One way of eliminating the above mentioned turbo lag, is to feed extraadditional air and by that additional fuel, to the engine during thistake-off phase or other load cases where engine response is required, inorder to increase the engine response and by that increase the exhaustenergy the turbo turbine which create the possibility of feeding extraair and fuel to the engine

For example, U.S. Pat. No. 6,138,616 discloses a valve arrangement in acombustion engine which is preferably equipped with a turbo unit, wherethe turbo function can be initiated earlier than in previously knowndevices and which adds to the starting torque of the engine. Inparticular, the valve arrangement comprises a secondary valve to supplyadditional air to the cylinder after the ordinary air supply from a mainvalve.

However, even though the disclosed apparatus provides a greatimprovement over prior art engines, there is still further room forimprovement of the apparatus described in U.S. Pat. No. 6,138,616. Thevalve arrangement comprises a valve guide with a two piece designincluding an upper valve guide portion and a lower valve guide portion.A cavity is defined between the upper valve guide portion and the lowervalve guide portion. This cavity is pressurized with compressed air whenadditional air is supplied via the secondary valve. This two-piecedesign of the valve guide require assembly with two different assemblytools in two separate operations followed by a reaming operation tosecure a coaxial relationship between a centre axis of the upper valveguide portion and a centre axis of the lower valve guide portion.

It is desirable to provide a valve arrangement creating conditions for amore efficient assembly of the valve arrangement.

According to an aspect of the invention, a valve arrangement is providedfor supplying air to an internal combustion engine, the valvearrangement comprising: a first valve for controlling an air supply to acylinder, the first valve being movable between a closed position inwhich the air cannot be supplied to the cylinder and an open position inwhich the air is supplied to the cylinder, the first valve comprising: afirst valve head, and a first valve stem comprising an inlet in a sidewall of the valve stem, wherein the inlet is configured to receiveadditional air from a feeder channel, the first valve stem furthercomprising an internal passage, arranged in the length direction of thevalve stem and fluidly connected to the inlet and configured to supplythe additional air to the cylinder; a second valve arranged within thefirst valve and configured to control the flow of additional air to thecylinder, the second valve comprising a second valve stem and a secondvalve head contacting an inner surface of the first valve head when thesecond valve is in a closed position; a tubular valve guide arranged tosurround a portion of the first valve stem such that the first valvestem is movable in the valve guide; characterized in that the valveguide comprises an inner groove forming a cavity between the valve guideand the first valve stem, wherein the valve guide further comprises avalve guide aperture configured to fluidly connect the inner groove tothe feeder channel, and wherein the inlet of the first valve stem isaligned with the valve guide aperture when the first valve is in aclosed position.

The definition that the valve guide is tubular should be interpreted tomean that the valve guide comprises an internal passage running alongthe length of the valve guide. Preferably, the internal passage has asubstantially circular cross sectional shape. Moreover, the internalpassage is adapted to match an outer dimension of the first valve stemsuch that the first valve stem is movable in the valve guide withoutthere being any significant gap between the valve stem and the valveguide. Preferably, the first valve stem has a circular cross sectionalshape defined by a diameter. The inlet of the first valve stem may alsobe referred to as a feeder hole, and the first valve stem may compriseone or more inlets, i.e. feeder holes. Moreover the first inlet valvemay be regarded as the main or primary inlet valve, supplying themajority of air to the cylinder.

Designing the valve guide with the inner groove and the aperture forminga communication between a feeder channel in an engine head and thegroove creates conditions for making the valve guide in a one-pieceunit. This in turn creates conditions for a time-efficient assembly inthat the valve guide may be positioned into its associated recess in theengine head via a single operation with a single assembly tool. Further,the valve guide design creates conditions for avoiding any additionalmachining after the positioning. Further, the valve guide design createsconditions for an accurate axial positioning of the groove relative tothe feeder channel in the engine head on the outside and the inlet ofthe first valve stem on the inside. Further, such a one-piece valveguide design creates conditions for a cost-efficient production of thevalve guide itself with proper tolerances.

According to one example, additional air is supplied to the cylinderfrom a compressed air tank when additional response is required from theengine, thus enabling an increased fuel amount to be supplied. This inturn generates a high increase in take-off performance, which eliminatesthe turbo-lag and the perception of the engine as being insufficientwith regard to the take-off torque. In particular, turbo-lag may beovercome by means of the valve arrangement in a compensation systembased on injection of pressurized air after main inlet valves areclosing. The system comprises an electronic controller that controls theengine and the air injection system according to the following methodsteps: determining an engine operating condition including the boostpressure in the inlet manifold and in the extra accumulator air tank ofcompressed air in conjunction to the engine; determining if compressedair pressure is sufficient in the extra accumulator air pressure tank;determining an amount and/or duration of compressed air to be injectedinto the cylinder after the inlet valves are closed; determining a fuelamount adjustment based on the addition of pressurized air, desiredair-fuel ratio, regulating/controlling the extra added air, after theinlet valves are closed, to a level near lambda 1 in air/fuel ratioand/or zero particulates is emitted in the engine out exhaust gases. Itis determined to end the extra injection of air based on whether theturbo pressure is sufficient to take over the supply of requested air,or whether the torque demand of the driver has decreased.

According to an embodiment of the invention, the valve guide is madefrom a single piece. In particular, the valve guide can be machined froma single piece of material which is enabled by improved manufacturingmethods. Thereby, the mechanical strength of the valve guide can beimproved. Furthermore, the assembly process is simplified for a valveguide made from a single piece and no additional machining is requiredafter the installation.

According to one embodiment of the invention, the inner groove isarranged to span the inner circumference of the valve guide. Thereby acavity with a maximum volume is achieved for a given width of thegroove, which in turn provides the largest possible addition of air tothe cylinder via the one or more inlets in the first valve stem.

According to one embodiment of the invention, the inlet in first valvestem is arranged such that when the first valve is fully open, the inletin the first valve stem is offset in relation to the valve guideaperture such that additional air is prevented from flowing from thefeeder channel into the cylinder. Thus, when the first valve is fullyopen, no additional air can flow from the tank to the cylinder, and onlythe first valve, i.e. the main inlet, provides air to the cylinder. Thisminimizes the consumption of compressed air during an activation.

According to one embodiment of the invention, the second valve isconfigured such that the second valve head, when in an open position,does not protrude past an end face of the first valve head. Thereby, thevalve arrangement can be used without having to adjust the valverecesses in the piston of the cylinder, since the second valve will notalter the outer geometry of the valve head of the first valve.

According to one embodiment of the invention, the valve arrangementfurther comprises a first spring connected to a first spring washer anda second spring connected to a second spring washer, wherein the firstspring acts to close the first valve and the second spring acts to closethe second valve. The first, outer, spring and washer are designed toprovide the closing force to the internal second valve. The closingforce thus contributes to the total closing force when the second valveis closed. The design means that the valve springs works independentlywhen required and as an assembly when both valves are open.

According to one embodiment of the invention, a closing force of thesecond spring is higher than an air pressure force of additional airprovided from said feeder channel. Thereby, additional air is preventedfrom flowing into the cylinder when the second valve is closed, even ifthe valve from the pressure tank is open so that additional pressurizedair is provided to the valve arrangement.

According to one embodiment of the invention, the valve guide apertureis arranged so that a lower edge of the valve aperture does not reachbelow a lower edge of the groove. The location and diameter of the valveguide aperture is so located so that it does not affect the lower edgein the groove, which is important to achieve the correct timing of whenthe compressed air starts to be injected. The relative location of thelower edge of the groove versus the location and the size of the inletof the first valve defines the timing and consumption of the air in theair injection.

There is also provided a vehicle or a stationary engine comprising avalve arrangement according to any one of the preceding embodiments.

According to an embodiment of the invention, there is provided an airsupply arrangement for a combustion engine, the air supply arrangementcomprising: a valve arrangement; a camshaft comprising a cam lobe,wherein the cam lobe is configured to control the first and secondconcentric valves such that the second valve opens prior to the openingof the first valve, and such that the second valve closes after thefirst valve has closed.

According to an embodiment of the invention the air supply arrangementfurther comprises a pressurized air tank for providing additional air afeeder channel fluidly connecting the air tank to the valve guideaperture; and a valve controlling the flow of air from the tank.

It is also desirable to provide a valve guide creating conditions for amore efficient assembly of a valve arrangement comprising the valveguide.

According to an aspect of the invention, a valve guide is provided forsurrounding a portion of a first valve stem such that said first valvestem is movable in said valve guide, wherein the valve guide is tubular,characterized in that said valve guide comprises a recess in an innersurface for forming a cavity between said valve guide and said firstvalve stem, and that said valve guide further comprises an aperturefluidly connecting said recess with an outer surface of said valveguide.

More specifically, the valve guide is adapted so that the first valvestem may be moveably arranged in its main extension direction in thevalve guide.

Designing the valve guide with the inner groove and the aperture forforming a communication between a feeder channel in an engine head withthe groove creates conditions for making the valve guide in a one-pieceunit. This in turn creates conditions for a time-efficient assembly inthat the valve guide may be positioned into its associated recess in theengine head via a single operation with a single assembly tool. Further,the valve guide design creates conditions for avoiding any additionalmachining after the positioning. Further, the valve guide design createsconditions for an accurate axial positioning of the groove relative tothe feeder channel in the engine head on the outside and the inlet ofthe first valve stem on the inside. Further, such a one-piece valveguide design creates conditions for a cost-efficient production of thevalve guide itself with proper tolerances.

According to one embodiment, said valve guide is a one-piece unit. Thiscreates conditions for a time-efficient assembly in that the valve guidemay be positioned into its associated recess in the engine head via asingle operation with a single assembly tool.

According to another embodiment, said recess forms a groove with a mainextension in a circumferential direction of said valve guide. The groovecreates conditions for a space-efficient structure for covering aplurality of circumferentially spaced inlets provided in the valve stem.According to one example, said recess forms a groove with a mainextension in a direction perpendicular to an axial direction of saidvalve guide. According to a further example, said groove forms acontinuous annular structure.

According to another embodiment, the recess is formed by machining theinner surface from an interior of the tubular valve guide. This createsconditions for a time-efficient production of the valve guide.

According to another embodiment, the aperture is positioned relative tothe recess so that a surface defining the recess in an axial directionof the valve guide is at the same distance or closer to a first end ofthe valve guide than surface defining said aperture at the connectionbetween the aperture and the recess. Thus, the aperture does not affecta lower edge of the recess defined by the surface defining the recess inthe axial direction of the valve guide, which is adapted for controllingthe timing of supply of the additional air to an associated cylinder.

According to another embodiment, the aperture is a hole with a circularcross section. It creates conditions for a time- and cost-efficientproduction, such as via drilling. According to one example, the apertureis therefore formed by a drilled hole.

According to another embodiment, an axis of the aperture isperpendicular to an axial direction of the valve guide.

According to another embodiment, said valve guide comprises a guidemeans adapted for guiding the valve guide to a circumferential positioninside of a housing in which the aperture coincides with a feederchannel. According to one example, said guide means is positioned at alower portion of the valve guide for engagement with an external toolduring assembly.

According to another embodiment, a first portion of the valve guidecomprising the aperture has a first diameter, and a second portion ofthe valve guide located adjacent to the first end of the valve guide hasa second diameter smaller than the first diameter, thereby forming atapered transition region between the first portion and the secondportion of the valve guide, and wherein the guide means is locatedwithin the tapered transition region. Thereby, the external tool can usethe tapered region as an identifier for where to locate the guide means.

According to another embodiment, the valve guide comprises a guide meansin the form of a notch in the above described tapered region. The notchhas a circumferential position aligned with a circumferential positionof the aperture. Thereby, the assembly tool can utilize the notch as aguide means during to ensure that the aperture is correctly aligned in avalve arrangement comprising the valve guide. In other words, since thenot is aligned with the aperture, the notch can be used to make surethat the aperture of the valve guide is aligned with an outlet of thefeeder channel providing additional air to the cylinder via the valvearrangement.

According to another embodiment, the valve guide further comprises analignment mark located between the aperture and a second end of thevalve guide, wherein the alignment mark is configured to be visible whenthe valve guide is assembled in a valve arrangement. By observing thealignment mark of the valve guide after the valve guide has beenarranged in the valve arrangement, it can be determined if the valveguide is located in the correct position such that the aperture isaligned with the feeder channel.

According to another embodiment, the alignment mark comprises a notchhaving a circumferential position aligned with a circumferentialposition of the aperture. A notch can be observed by means of a visualinspection, where it can be verified that the notch of the valve guideis aligned with a corresponding alignment mark of the valve arrangementin which the vale guide is mounted. However, the alignment mark of thevalve guide may also be formed as an etch mark, an inscribed mark, orany other type of visually identifiable marking on the valve guide.

The invention further relates to a valve arrangement for supplying airto an internal combustion engine, the valve arrangement comprising: afirst valve for controlling an air supply to a cylinder, the first valvecomprising: a first valve head and a first valve stem; a valve guideaccording to any one of the alternatives above arranged to surround aportion of the first valve stem such that the first valve stem ismovable in the valve guide.

According to another embodiment, the first valve stem comprising aninlet in a side wall of said valve stem, wherein said inlet isconfigured to receive additional air from a feeder channel via theaperture and the recess of the valve guide.

According to a further development of the last-mentioned embodiment,said first valve stem further comprising an internal passage arranged inthe length direction of said valve stem and fluidly connected to saidinlet and configured to supply said additional air to said cylinder.

According to a further development of the last-mentioned embodiment, thevalve arrangement comprises a second valve arranged within said firstvalve and configured to control the flow of additional air to saidcylinder, said second valve comprising a second valve stem and a secondvalve head.

Further advantages and advantageous features of the invention aredisclosed in the following description and in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a more detaileddescription of embodiments of the invention cited as examples.

In the drawings:

FIGS. 1A and 1B illustrate different types of vehicles equipped with avalve arrangement according to an embodiment of the invention;

FIG. 2 schematically illustrates a valve arrangement according to anembodiment of the invention;

FIGS. 3A and 3B schematically illustrate a valve guide according to anembodiment of the invention;

FIGS. 4A-E schematically illustrate different stages of a cycle of avalve arrangement according to an embodiment of the invention;

FIG. 5A schematically illustrates a cross section of a camshaft lobewhich can be used in connection with an embodiment of the invention;

FIG. 5B schematically illustrates a resulting lift curve when using avalve arrangement according to an embodiment of the invention; and

FIG. 6 schematically illustrates an air supply arrangement according toan embodiment of the invention.

DETAILED DESCRIPTION

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which currently preferredembodiments of the invention are shown. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided for thoroughness and completeness, and fully convey the scopeof the invention to the skilled addressee. Like reference charactersrefer to like elements throughout.

Referring now to the drawings and to FIGS. 1A, 1B, and 2 in particular,there is in FIG. 1A depicted an exemplary vehicle, here illustrated as atruck 100 comprising an engine in which a valve arrangement according tothe present invention may be incorporated. The valve arrangement may ofcourse be implemented also in a car 100′, as shown in FIG. 1B, a workingmachine or in any engine, such a stationary engine, having a supply ofcompressed air.

The valve arrangement can be used in a combustion engine, such as aconventional turbocharged diesel engine. In particular, each cylinder ofthe engine may comprise a valve arrangement according to embodiments ofthe invention.

According to one exemplary method of operation, additional air is feddirectly into the cylinders of an engine in connection with the take-offphase or when additional response from the engine is required, i.e.during the initial phase when it functions as an aspirating engine. Thisadditional air is fed via a plurality of air passages, which lead up tothe different cylinders. The feeding of ordinary and additional air tothe different cylinders is done by means of at least one special valvearrangement which is provided at each of the different cylinders.Further details concerning such a valve arrangement and an enginecomprising such a valve arrangement can be found in U.S. Pat. No.6,138,616, hereby incorporated by reference.

Referring now to FIG. 2, the engine comprises a valve arrangement 200arranged at an intake 202 of each cylinder of the engine. The intake 202is used for feeding ordinary air to the cylinder. At the point where theintake 202 enters the cylinder, there is arranged a valve seat 204against which a first valve 206 is arranged. To this end, the firstvalve 206 comprises a first valve head 208, which is in contact with alower, essentially circular edge 210. The first valve head 208 isconnected to a first valve-stem 212, which runs in an essentially jacketshaped valve guide 214. The function of the first valve 206 correspondsto the ordinary valve function of a diesel engine for the supply ofordinary air to the combustion in the different cylinders.

Using the force from an external valve spring 216 and an internal valvespring 218, the first valve head 208 is influenced to be in contact withthe valve seat 204. To be more exact the first and second, external andinternal, valve springs 216, 218 are in contact with, and press against,first and second, external and internal, spring washers 220, 222,respectively, where the second spring washer 222, via a valve lock, isin connection with the first valve-stem 212. The lower part of the firstvalve stem 212 is essentially tube-shaped, and comprises an internalpassage 224 extending in a longitudinal direction of the valve stem 212.The internal passage 224 is widened at its lower end. The internalpassage 224 houses a second valve 226 with a second valve head 228 whichis in contact with a further valve seat in the form of an inner surface230 of the first valve head 208. The second valve head 228 isfurthermore connected to a second valve stem 232 which has its extensioninside the passage 224.

The upper part of the first valve stem 212 is shaped with athrough-going passage-section 234, the inner dimensions of whichessentially correspond to the outer dimensions of the second valve stem232. The internal passage 224 in the lower part of the first valve stem212 has a diameter which is larger than the diameter of the second valvestem 232 to allow a flow of additional air in said internal passage 224.There is furthermore arranged along the circumference of the first valvestem 212 at least one inlet 236, and especially a plurality ofcircumferentially spaced inlets. According to the example, three inletsare arranged equidistantly in the circumferential direction of the firstvalve stem 212.

FIGS. 3A-B schematically illustrate the valve guide 214. The valve guide214 is tubular. The valve guide 214 comprises a recess 238 in an innersurface 244 for forming a cavity between the valve guide 214 and thefirst valve stem 212. The valve guide 214 further comprises an aperture242 fluidly connecting the recess 238 with an outer surface 246 of thevalve guide 214. The valve guide 214 is a one-piece unit.

The recess 238 forms a groove with a main extension in a circumferentialdirection of the valve guide 214. More specifically, recess 238 forms agroove with a main extension in a direction perpendicular to an axialdirection of the valve guide 214. More particularly, the groove 238forms a continuous annular structure. In other words, the inner groove238 can be seen to span the inner circumference of the valve guide.According to one example, the recess 238 is formed by machining theinner surface 244 from an interior of the tubular valve guide 214.

The valve guide aperture 242 is positioned relative to the recess 238 sothat a surface 250 defining the recess in an axial direction 256 of thevalve guide 214 is at the same distance or closer to a first end 252 ofthe valve guide 214 than a surface 248 defining the aperture 242 at theconnection between the aperture 242 and the recess 238. In other words,the lower edge of the aperture 242 does not reach below the lowerportion of the groove 238. Further, the aperture 242 is a hole with acircular cross section. More specifically, the aperture 242 is formed bya drilled hole. Preferably, an axis of the aperture 242 is perpendicularto an axial direction of the valve guide 214.

Further, the valve guide 214 comprises a guide means 258 adapted forguiding the valve guide to a circumferential position inside of ahousing in which the aperture 242 coincides with a feeder channel 240.Especially, the guide means 248 is positioned at a lower portion of thevalve guide 214 for engagement with an external tool during assembly.

Furthermore, a first portion 260 of the valve guide comprising theaperture 242 has a first diameter, and a second portion 262 of the valveguide located adjacent to the first end 252 of the valve guide has asecond diameter smaller than the first diameter, thereby forming atapered transition region 264 between the first portion 260 and thesecond portion 262. The guide means 258 is here embodied by a triangularnotch 258 in the tapered region, wherein the notch 258 has acircumferential position which is aligned with a circumferentialposition of the aperture 242. The notch 258 has a flat surface in adirection parallel with the axial direction 256 of the valve guide 214,such that an engagement member of an assembly tool can be moved towardsthe surface of the notch 258 and recognize when the engagement membermakes contact with the flat surface. Thereby, the assembly tool canverify that the valve guide is in the correct position before thepressing the valve guide into the cylinder head. The guide means 258 mayalso have the form of groove, a trench or the like allowing theengagement of an external tool during assembly of a valve arrangement.

The valve guide also comprises an alignment mark 266 located between theaperture 242 and a second end 254 of the valve guide, wherein thealignment mark is configured to be visible when the valve guide isassembled in a valve arrangement. The alignment mark 266 is hereillustrated as a notch 266 having a circumferential position alignedwith a circumferential position of the aperture 242.

A feeder channel 240 is connected to the cavity defined by the recess238 via the valve guide aperture 242 arranged in the side wall of thevalve guide 214. It is preferable that the resulting ellipsoid openingof the feeder channel 240, adjacent to the valve guide aperture 242, iscompletely covered by the valve guide aperture 242. Moreover, the groove238 is aligned with the valve guide aperture 242 configured to connectthe cavity formed by the groove 238 to the feeder channel 240.

In the normal position of the valve arrangement 200, i.e. when the firstvalve 206 is in contact with the valve seat 204 and the second valve 226is in contact with the inside of the first valve head 208, the cavityformed between the groove 238 of the valve guide 214 and the first valvestem 212 is aligned with the at least one inlet 236 in the first valvestem 212. In order to connect additional air to the cylinder there isfurthermore provided a drilled feeder channel 240 which terminates atthe valve guide aperture 242 in the valve guide 214.

As will be described in detail below, air can be supplied to the feederchannel 240 via a control valve and further on to the lower internalpassage 224 of the first valve stem 212. The additional air is thus ledtowards the engine cylinder via the second valve 226 which iscontinuously opened and closed by the camshaft, as will be describedbelow. The second valve-stem 232 is at least along a certain sectiondimensioned so as to be a good fit against the lower end of the upperpassage-section 234. This enables transfer of heat between the secondvalve-stem 232 and the first valve stem 212, at the same time as itprovides a sealing function which prevents air from flowing upwardsalong the upper passage-section 234. It also protects the secondvalve-stem 232 from the risk of buckling, especially during high enginespeed operation.

The function of the valve arrangement will now be described withreference to FIG. 2 and FIGS. 4A-E which schematically illustrate thedifferent stages when supplying air to the different cylinders. FIGS.4A-4E show the intake stroke in a cylinder 302 which is equipped withthe valve arrangement 200 according to the invention. As is first shownin FIG. 4A, the piston 304 of the cylinder 302 is in its upper positionin the cylinder 302. The piston 304 is, in a conventional mannerconnected to the crankshaft 306 via a connecting rod 308. In this upperposition the first valve 206 is in contact with the valve seat 204 dueto the spring-force from the spring 218. Furthermore, the second valve226 is in contact with the inside 230 of the first valve head 208 due tothe spring-force from the spring element 216.

In the next phase, as shown in FIG. 4B, the piston 304 moves downwards.At the same time the valve arrangement 200 is influenced by the camshaftof the engine (not shown). Thus, the spring-force of the external spring216 will first be exceeded, which leads to the second valve 226 beingpressed a small distance downwards, whereby the second valve head 228 islifted out of contact with the inside 230 of the first valve head 208.If the conditions for feeding additional air via the feeder channel 240are fulfilled, and air has been fed to the internal passage 224, amarginal amount of additional air will now during a short time be fed tothe cylinder 302, until the inlet is blocked by the lower part of thevalve guide as a consequence of the opening of the first valve 206, i.e.the main inlet valve. Here, it can also be seen that the second valvehead 228, when in an open position, does not protrude past an end faceof the first valve head 208.

FIG. 4C shows the following phase in which the piston 304 is on its waydown and the first valve 206 has been lifted out of the valve seat 204.At this phase, the ordinary air is aspirated into the cylinder 203 viathe intake 202 in the cylinder head. Furthermore, the first valve-stem212 has been displaced/opened a distance downwards relative the valveguide 214. This means that the at least one inlet 236 is no longeraligned with the groove 238 or the valve guide aperture 242, whichcauses the feeder channel 240 to be out of communication with theinternal passage 224 of the first valve 206. This in turn means that noadditional air is supplied during this phase, when the first valve 206is open.

In the next phase, which is shown in FIG. 4D, the piston 304 has justpassed its lowest position and is on its way upwards in the beginning ofthe compression stroke. Furthermore, the camshaft of the engine hasinfluenced the valve arrangement 200 to be moved towards its initialposition, so that the first valve 206 is now closed, i.e. the firstvalve head 208 is in contact with the valve seat 204. According to theinvention, the camshaft is so arranged that the second valve head 228has not yet come into contact with the first valve head 208, i.e. thesecond valve 226 is still open. Furthermore, the first valve-stem 212 inthis phase is in such a position that the at least one inlet 236 isessentially aligned with the groove 238, which causes additional air tonow be fed to the cylinder 302 via the passage defined by the internalpassage 224. In this way, the first valve 206 will thus be closed andthe second valve 226 will be open for the supply of additional air,which takes place during the beginning of the compression phase andafter the first valve 206 is closed. The duration of this sequence ofevents (i.e. the supply of additional air) is controlled by the shape ofthe inlet lobe of the camshaft, as will be described in detail below inrelation to FIG. 5A. The duration also depends on the positioning of theinlet 236 in relation to the groove 238.

Finally, FIG. 4E shows that the second valve stem 232 and thus also thesecond valve head 228 has been released upwards, so that the secondvalve 226 is closed, i.e. the second valve head 228 is in sealingcontact with the inside 230 of the first valve head 208. The springelement 216 is here so dimensioned that its spring-force, which attemptsto close the second valve 226, exceeds the force with which the airpressure in the internal passage 224 affects the second valve 226.Subsequent to this final phase, the compression stroke is in a knownmanner started and a larger amount of fuel can be supplied, since acertain amount of additional air now has been fed into the cylinder 302.

FIG. 5A shows a schematic cross-section of a camshaft 502 which can beused in connection with the invention. In a way which as such is known,and which is not shown in detail, the engine is used to drive thecamshaft 502. The camshaft 502 affects a valve lifter 504, which in turncauses the valve arrangement 200 to open and close. FIG. 5A shows theradius r₁ of the camshaft 502 with a solid line, while the radius r₂ ofa basic circle is indicated with a broken line. FIG. 5A also shows inprinciple five different angle-sectors S₁, S₂, S₃, S₄, S₅, whichcorrespond to the different phases as shown in FIGS. 4A-E. Angle-sectorS₁ thus corresponds to what is shown in FIG. 4a i.e. the valvearrangement 200 is closed, i.e. both the first valve 206 and the secondvalve 226 is closed. Angle-sector S₂ corresponds to what is shown inFIG. 4B i.e. the second valve 226 is open while the first valve 206 isclosed. A marginal addition of air to the cylinder takes place during ashort amount of time here when air is supplied. Furthermore,angle-sector S₃ corresponds to that shown in FIG. 4C, i.e. the firstvalve 206 is open but no additional air is supplied since the inlet 236is not aligned with the groove 238. During angle-sector S₄ the firstvalve 206 starts to close. Finally, angle-sector S₅ corresponds to FIG.4D, i.e. a position where the first valve 206 is closed but the secondvalve 226 is still kept open. This angle-sector S₅ in this manner formsa “plateau” with an essentially constant radius of the camshaft 502 withadditional air being supplied to the different cylinders. By varying thesize of this angle-sector us, the period of time during which additionalair is supplied can be varied, thereby controlling the lift curve of thevalve arrangement. The disclosed valve lift curve is a unique low costfeature for the valve arrangement according to embodiments of theinvention to maneuver two functions with one modified lift curve formaximum synchronization and control of the motion between the twovalves.

FIG. 5B schematically illustrates a lift curve (solid) for the camshaft502 described in FIG. 5A. The lift curve is compared to a lift curve(dashed) for a conventional camshaft. FIG. 6 schematically illustratesan air supply arrangement 600 comprising a pressurized air tank 602 forproviding additional air to the cylinder. The flow of air from thepressurized air tank 602 to the feeder channel 240 is controlled by avalve 604 arranged on the air supply line 606. Thereby, the valve can becontrolled so that additional air is only supplied to the cylinderduring selected load cases when the addition of air is required.

It is to be understood that the present invention is not limited to theembodiments described above and illustrated in the drawings; rather, theskilled person will recognize that many changes and modifications may bemade within the scope of the appended claims. The invention can forexample be used in different kinds of combustion engines, e.g. dieselengines and gasoline engines. The invention is furthermore not limitedto use in connection with turbocharged engines, but can also be used forsupplying additional air in engines without turbo units.

The invention claimed is:
 1. A valve arrangement for supplying air to aninternal combustion engine, the valve arrangement comprising: a firstvalve for controlling an air supply to a cylinder, the first valve beingmovable between a closed position in which the air cannot be supplied tothe cylinder and an open position in which the air is supplied to thecylinder, the first valve comprising: a first valve head, and a firstvalve stem comprising an inlet in a side wall of the first valve stem,wherein the inlet is configured to receive additional air from a feederchannel, the first valve stem further comprising an internal passage,arranged in the length direction of the valve stem and fluidly connectedto the inlet and configured to supply the additional air to thecylinder; a second valve arranged within the first valve and configuredto control the flow of additional air to the cylinder, the second valvecomprising a second valve stem and a second valve head in contact withan inner surface of the first valve head when the second valve is in aclosed position; a tubular valve guide arranged to surround a portion ofthe first valve stem such that the first valve stem is movable in thevalve guide; wherein the valve guide comprises an inner groove forming acavity between the valve guide and the first valve stem, wherein thevalve guide further comprises a valve guide aperture configured tofluidly connect the inner groove to the feeder channel, and wherein theinlet of the first valve stem is aligned with the valve guide aperturewhen the first valve is in a closed position.
 2. The valve arrangementaccording to claim 1, wherein the valve guide is made from a singlepiece.
 3. The valve arrangement according to claim 1, wherein the innergroove is arranged to span the inner circumference of the valve guide.4. The valve arrangement according to claim 1, wherein the inlet in thefirst valve stem is arranged such that when the first valve is fullyopen, the inlet in the first valve stem is offset in relation to theaperture of the valve guide such that additional air is prevented fromflowing from the feeder channel into the cylinder.
 5. The valvearrangement according to claim 1, wherein the second valve is configuredsuch that the second valve head, when in an open position, does notprotrude past an end face of the first valve head.
 6. The valvearrangement according to claim 1, further comprising a first springconnected to a first spring washer and a second spring connected to asecond spring washer, wherein the first spring acts to close the firstvalve and the second spring acts to close the second valve.
 7. The valvearrangement according to claim 6, wherein a closing force of the secondspring is higher than an air pressure force of additional air providedfrom the feeder channel.
 8. The valve arrangement according to claim 1,wherein the valve aperture is configured so that a lower edge of thevalve guide aperture does not reach below a lower edge of the groove. 9.A vehicle or a stationary engine comprising a valve arrangementaccording to claim
 1. 10. An air supply arrangement for a combustionengine, the air supply arrangement comprising: a valve arrangementaccording to claim 1; a camshaft comprising a cam lobe, wherein the camlobe is configured to control the first and second valves such that thesecond valve opens prior to the first valve, and such that the secondvalve closes after the first valve has closed.
 11. The air supplyarrangement according to claim 10, further comprising: a pressurized airtank for providing additional air; a feeder channel fluidly connectingthe air tank to the valve guide aperture; and a valve controlling theflow of air from the tank.